Photocurable resins comprising hydrophobic polymer systems to be subjected to photodimerization for crosslinking have so far been used in lithography, paints and printing, among others. On the contrary, there are few examples known where hydrophilic polymers are photocrosslinked.
On the other hand, attempts have been made to crosslink GAGs, which are typical hydrophilic polymers, by means of aldehydes, epoxy compounds, divinyl sulfone compounds and the like for prolonging the actions of GAGs in vivo or for preparing materials for medical use in the form of films or powders, for example for preventing tissue adhesion. However, since GAGs are macromolecules, the crosslinked GAG derivatives formed are still higher in molecular weight and this fact makes it difficult to completely remove unreacted materials and/or catalysts from the crosslinked GAG derivatives. Thus, when administered to or implanted into living bodies, said derivatives may frequently produce adverse effects, so that they are not suited for practical use. In addition, crosslinked GAG derivatives occur as gels or solids and therefore are difficult to mold after crosslinking, hence not suited for practical use. Furthermore, as for their use as carriers in sustained or controlled release drug preparations (JP-A-62-129226 corresponding to U.S. Pat. No. 5,128,326; the term "JP-A" used herein means an unexamined published Japanese patent application), sustained release of active ingredients can be attained only by taking advantage of the viscous property of crosslinked GAG derivatives and this disadvantage renders them unsuited for practical use. Thus, such methods and crosslinked GAG derivatives can hardly control the rate of release of drugs.
It is also known that photosensitive materials prepared by esterifying hydroxyl groups of microorganism or plant derived polysaccharides such as pullulan, amylose and mannan with cinnamoyl groups which are photodimerizable functional groups are usable as adsorbents, enzyme carriers or carriers for chromatography or in producing PS plates or photoresists or for other applications [JP-B-56-14969 corresponding to U.S. Pat. No. 3,960,685 (the term "JP-B" used herein means an examined published Japanese patent application), JP-A-60-219202].
However, the photosensitive materials mentioned above have a problem in securing safety, can hardly control cell adhesion and are poor in biocompatibility in humans and, therefore, they are not suited for use as medical materials to be directly applied to living bodies, in particular artificial organs, medical products to be used for covering wounds or in surgery, carriers in pharmaceutical preparations, or other materials to be used for some or other medical treatment.